/Engine/Source/Runtime/Engine/Public/Animation/NamedValueArray.h
Helper function Uses a simple 'tape merge' Performs an operation per-element on the two value arrays. Writes result to OutResultValueArray. OutResultValueArray will be the union of the two value arrays after the operation is completed. InPredicate is called on all elements that are added to OutResultValueArray, with appropriate flags.
template<typename PredicateType, typename AllocatorTypeResult, typename ElementTypeResult, typename AllocatorType0, typename ElementType0, typename AllocatorType1, typename ElementType1> static void Union ( [TNamedValueArray](API\Runtime\Engine\Animation\TNamedValueArray)< AllocatorTypeResult, ElementTypeResult > & OutResultValueArray, const [TNamedValueArray](API\Runtime\Engine\Animation\TNamedValueArray)< AllocatorType0, ElementType0 > & InValueArray0, const [TNamedValueArray](API\Runtime\Engine\Animation\TNamedValueArray)< AllocatorType1, ElementType1 > & InValueArray1, const PredicateType & InPredicate )